Study On Emergency Repair Technology Of Subgrade Missing Disaster In Plain And Hilly Area

China has a vast territory and the highway network is increasingly dense.By the end of 2016,the total length of highways in China was 4.696 million kilometers.China is also a country frequently influenced by flood disasters.About 24% of road sections are frequently and severely hit by floods.Covered by plain and hilly areas,about two-fifths of China’s total land area has a subtropical monsoon climate in general.Summer rainfall in the area is abundant and the rainy season usually is concentrated from April to September.Long rainy periods and heavy rainfall contribute to the external source for disasters such as road base deficiency.There are many road base forms in plain and hilly areas,and frequent flood disasters occur from time to time.This provides internal and external conditions for unexpected situations such as road base deficiency.Although the highway disaster prevention and reduction work has already attracted the attention of the highway construction and management departments,the corresponding measures taken by the departments,after the sudden flood season and flood damages,remain to be general construction projects as a passive way of disaster management.The technical management needs to be improved and further targeted,and the lack of emergency recovery techniques for the affected road sections cannot meet the urgent needs of economic construction and national defense readiness security put forward after the 19 th National Congress of the CPC.Emergency disaster restoration is also a critical issue that needs to be solved urgently in the “Belt and Road” national strategy.This paper mainly focuses on the internal mechanism of road base deficiency in plain and hilly areas and the corresponding emergency recovery technology,which is a major socially beneficial technology issue.Field survey observations as well as research methods usually used in rock and soil mechanics,fluid mechanics,hydraulics,structural mechanics and other disciplines are carried out in this research to analyze the start-up particle condition and start-up speed for the occurrence of subsurface erosion seepage from the inside of the road base soil.In the cases of road base deficiencies that occur in different road base forms,corresponding emergency recovery techniques were developed according to the characteristics of disasters.The emergency recovery techniques were analyzed mechanically and simulated using a MIDAS numerical simulation software.A comprehensive research was carried out onthe emergency recovery techniques,and the research strives to put the techniques into use in actual rescuing and disaster reliefs to ensure the safety of people’s lives and property and national interests.Results are as follow:(1).The data collection was conducted on the topography and land forms of the plain and hilly areas and rainfall data in several major cities in the region.The classification of the water damage status was detailed in this research.(2).After an analysis of disaster characteristics and damage patterns of the road base deficiency in the plain and hilly area,based on disciplines of fluid mechanics,hydraulics and soil mechanics,a formula of critical starting velocity for seepage in different directions of seepage subsidence is deduced.The formula for the particle radius requirement is determined according to the movement of fine particles in the capillary model.(3).Aiming at road base deficiencies in hanging road sections,corresponding emergency recovery techniques were developed and optimized on the basis of initial calculation.The working principle of self-anchor type emergency bolt was analyzed using structural mechanic and material mechanic devices,and the calculation formula was confirmed.Finally,the stability of the entire anchorage structure is analyzed and simulated by a numerical simulation software MIDAS.(4).To tackle with the deficiency of road base in a whole section,an emergency recovery technique,steel sheet pile cofferdam backfilling,was put forward,and on the basis of it,the semi-circular steel pipe sheet pile cofferdam was optimized.Mechanical calculation and detailed construction process were carried out referring to actual examples.